Capacitive touch screens are well known in the art. FIG. 1 illustrates a basic block diagram of such a capacitive touch screen 10 which comprises a touch screen panel 12 formed to include a plurality of drive (or force) lines 14 extending in a first direction and a plurality of sense lines 16 extending in a second direction which is generally oriented perpendicular to the first direction. A sensing cell 18 is formed at each location where a drive line 14 crosses a sense line 16. In this regard, a mutual capacitance is formed at each sensing cell between the drive line 14 and sense line 16.
A drive circuit 20 is configured to sequentially apply a drive signal to each of the drive lines 14. A sensing circuit 22 is coupled to the sense lines 16 and is configured to sense the mutual capacitance at each of the sensing cells 18. In the case where a touch or proximate touch is made to the touch screen panel 12 by a user's finger (or other body part) or a stylus (for example, in the format of a pen), there is a change in the value of the mutual capacitance at one or more of the sensing cells 18. This change in capacitance is detected by the sensing circuit 22.
A processing circuit 24 receives the sensed capacitance information from the sensing circuit 22 and, with knowledge of the sequential application of the drive signals by the drive circuit 20, operates to interpret the sensed capacitance information to make a detection of a touch or proximate touch being made to the touch screen panel 12 based on the sensed change in capacitance.
In many instances, the use of a stylus, instead of a user's finger, provides an advantageous touch mechanism for touch screen applications. For example, the stylus will provide a smaller touch or proximate touch detection area than a user's finger, and thus provides for a more accurate (or focused) control over system operation.
Generally speaking, two types of stylus are used in capacitive touch screen systems. The first type is a passive stylus which is essentially a “small” or “pinpoint” finger. The advantages of such a passive stylus include minimal cost with enhanced touch screen sensitivity, as well as ease of replacement or substitution. A known disadvantage is the inability to detect pressure of the touch (or contact) made to the capacitive touch screen. The second type is an active stylus which advantageously presents enhanced touch screen sensitivity along with the ability to detect application pressure (contact). However, the active stylus is significantly more expensive, hard to replace, and is a product which consumes battery power in use.
Notwithstanding the drawbacks experienced with active stylus implementations, the consumer market is moving towards adoption of this technology in connection with many products that use capacitive touch screen systems (such as smart phones, tablet computers, and the like). Thus, there is a need in the art for an improved stylus of an active-type for use in capacitive touch screen applications. The embodiments disclosed herein provide such an improved stylus configuration with enhanced functionality along with an associated system including a touch screen and stylus in operational combination.